Metal recovery method



Aug. 23, 1969 i. w. Pam 3,433,633

- METAL RECOVERY METHOD Filed Marh 1, 1967 ,wif/ Maya/Ww V//Jf /ff/ ff/r4.4 falaz/M5@ 5 /sye a/f/ 14a/aas M /5 @Maf/V535@ aar wrm 4 Y N\v swffaaf aaai/Maza l aar 3 me W P5777/ INVENTOR.

United States Patent O 3,463,633 METAL RECOVERY METHOD Jack W. Petty, 1115 Arbor Dell Road, Los Angeles, Calif. 90041 Continuation-impart of application Ser. No. 534,858,

Mar. 16, 1966. This application Mar. 1, 1967, Ser. No. 619,664

Int. Cl. C22b 11/02, 11/10; C10b 57/04 U.S. Cl. 75-83 12 Claims ABSTRACT F THE DISCLOSURE A metal recovery method in which oil shales are heated to drive off oily vapors, and the oily vapors are bubbled .through a molten metal with which precious metals will combine.

`Cross references to related applications This application is a continuation-impart of copending application Ser. No. 534,858 for Metal Recovery Method filed by me Mar. 16, 1966 now abandoned. The benefit of the date of said copending application is there- -fore hereby claimed for this application.

Background of the invention This invention relates to the metallurgical art and more particularly to a method of recovering metals from oil shales (Kerogen), tar sands, carbonaceous material, and natural petroleum. When oil shales are mentioned hereinafter, tar sands, natural petroleum, and carbonaceous materials are included in this phrase.

Although the present invention should not be limited t0 those uses specifically described herein, it has been found to have exceptional utility in recovering gold, silver, and other precious metals from vapors, gases, entrained liquids and solids obtained by heating and retorting oil shale (Kerogen), tar sands, carbonaceous materials, and natural petroleum. When the term vapors is mentioned hereinafter, it is taken also to include gases, entrained liquids, and solids. It has been discovered that such vapors contain gold an-d silver.

Summary of the invention In accordance with the present invention, gold and silver are removed from such vapors to reduce production costs of petroleum compounds. The method of the inven- -tion includes the step of contacting a metal in a liquid state with an -oily vapor derived from oil shale wherein the the metal has the capacity of alloying with the metal to be recovered.

The above-described and other advantages of the present invention will be better understood from the following description when considered in connection with the acpanying drawings.

Brief description of the drawing In the drawing, the view is diagrammatic of the apparatus employed with the method of the present invention.

Description of the preferred embodiments In the drawing, an oil shale retort 3` is located in a furnace #1. Retort 3 has an inlet passageway `4 and an outlet passageway 5. Shale is heated in retort 3 and vapors collected and transmitted via a pipe 6 to the bottom of a bubble tower 7 containing a molten metal. Tower 7 has an inlet at 8 and an outlet at 9. A condenser 10` is provided to condense oily vapors that are pressed from tower 7 to condenser 10. Bubble tower 7 is heated in a furnace #2.

In the tube leading from the bubble tower 7 to condenser 10, a vacuum pump 13 is incorporated. The vacuum pump 13 is used to facilitate the ilow of oily vapors 3,453,633 Patented Aug. 26, 1969 ICC through the molten metal. Also, after passage through the molten metal, oily vapors are quickly transferred to the condenser, thereby reducing the tendency of the oily vapor to form coke in the bubble tower above the molten metal.

At a convenient place in the bubble tower near the bottom, provision is made to circulate the molten metal by means of a suitable pump 12 through a lter 11 to remove carbon, coke, adventitious mineral particles, and the like which may enter the system from the retort. The ltered molten metal is returned to the bubble tower at a convenient point above the molten metal level in the bubble tower.

Y Types of retorts other than retort 3, such as the U.S. Bureau of Mines gas combustion type, Union Oil Company rock pump gas combustion retort, etc., which depend upon partial burning of the oil shale may also be used. The oily vapors and combustion products `formed are collected at the retort vapor exit 6 and then through tube 6 into the molten metal bath. Another suitable method is to maintain a partial vacuum in the bubble tower so that oily vapors, etc. are drawn through the molten metal.

In the event natural petroleum is being processed, hot vapors, liquids, etc. from the pipe still are forced through the molten metal in the bubble tower. However, the temperatures employed are generally in the range of 400 F. to l000 F. or more. After passage through the molten metal, the vapors and hot petroleum are led into a fractionating column for further processing. See also Petroleum Products Handbook, Virgil B. Guthrie (McGraw-Hill, lst edition, 1960, pages l-1l).

The molten metal in tower 7 may be one or more of metals in Groups l-B, 2-B, 3-A, 4-A, and 5-A of the periodic table as set forth on page 59 of Handbook of Chemistry, Sixth Edition, by N. A. Lange (Handbook Publishers, Inc., 1946, Sandusky, Ohio).

Alternatively, the metal in tower 7 may actually be two or more metals. These metals may be in the said groups of the periodic table aforesaid. For example, tin and aluminum may be used together. Zinc and aluminum may also be used together.

Example Oil shale is heated in retort 3` to a temperature of 850 F. or more. The oil shale temperature should be suiciently high to drive off oily vapors and yet be low enough to minimize breakdown of the oily vapors. Tin is then used in tower 7. It is heated to a temperature of 450 F. or more, its melting point being 450 F.

It will be noted that the temperatures employed in Kerogen retorting for this or any other embodiment of the invention are not critical although best results are obtained within the range of 850 F. to 1700 F. or more, such as that obtained in gas combustion retorts. However, the temperatures at which oily vapors exit retort 3 may be as low at F.

When zinc is used, it is preferably heated to a temperature in excess of 790 F The melting point of zinc is 787 F. When lead is used in tower 7, it is heated to a temperature of 625 F. or more, its melting point being 622 F.

When aluminum is used in tower 7, itis preferably heated to a temperature of 1250 F. or more. If desired, Aluminum Corporation of America, Aluminum casting alloy #ABZ-T551, may be used; the melting point of this alloy is in the 1000 F. to 1050 F. range. None of the metal temperatures listed herein are critical. They simply need be maintained in a molten state.

It is preferred that tin, lead or aluminum be used in retort 7 because tin, lead, or aluminum readily alloy with a large number of metals.

After petroleum vapors have been bu'bbled through the molten metal in tower 7, the molten metal is drawn off at 9 and allowed to cool to a hardened state. Gold and silver may be recovered from the alloy which is removed from tower 7. Gold and silver in the product may then be refined in any conventional manner. One method of separating gold and silver from tin is by electrolysis. The tin may be plated out electrically, gold and silver values being recoverable from the resultant sludge or mud of the electrolyte bath.

When mercury is used, it may be injected directly into retort 3 and vaporized along with the oily vapors. Mercury has a boiling point of 675 F. In that event, the product may be condensed conventionally and gold and silver may be refined in a conventional way from the mercury recovered in the condenser.

The economics of the inventive process are attractive. For example, Colorado shale oil has a gold and silver content of approximately fifty cents per barrel. Brea, Calif., natural petroleum approximately twenty-tive cents per barrel, and Santa Maria, Calif., tar sands approximately fortysix cents per barrels. It is my experience that when proceeding in accordance with the invention, a substantial proportion of the gold and silver contained in the Kerogen content of the oil shale appears in the oily vapors issuing from the retorting process, and, in turn, a substantial portion of `that is captured by the molten metal and eventually made available as saleable metallic gold and silver. It may be observed that my inventive process can be carried out with no real interference with conventional methods for recovering oil from oil shale, and from the standpoint of heat consumption, the operating costs are low indeed. The metal used can readily be recovered substantially completely from the step wherein the gold and silver is extracted so as to make-up quantities from the System as a whole are low. It will be appreciated that my process is equally adaptable to processes in which oil shale is retorted and the oil therefrom is not necessarily recovered as a valuable constituent per se. This may occur with oil shales of high gold and silver content and relatively undesirable oily constituents, or where the retorted shale is the primary product of the process, being useful, for example, as a lightweight aggregate -for concrete or for solid fuel.

It is not uncommon to operate retorts for vaporizing oil from shale at temperatures such that the vapors and mists exit a retort at less than 200 F. Precious metal recovery may be made from such vapors and mists exiting at these lower temperatures. At the same time, the metals used in bubble tower '7 may be selected for a low melting temperature. For example, bismuth, lead, tin and cadmium and especially alloys thereof may have melting temperatures in the range of 117 F. to 479 F. Such metals and alloys may thus be used to advantage in bubble tower 7 in accordance with the present invention.

I claim:

1. A method of recovering a precious metal which is gold or silver comprising the steps of: contacting a molten bath containing at least one alloy [from the low melting point metals bismuth, lead, tin or cadmium with an oily vapor containing the precious metal to remove said precious metal from said oily vapor; and recovering the precious metal from the bath.

2. A method of obtaining a precious metal, said method comprising heating a precious-metal-bearing oil shale to drive off oily vapors which contain said precious metal; bubbling said vapors through a molten metal selected from the class consisting of metals in Groups l-B, 2-B, 3-A, 4-A and 5-A of the Periodic Table and mixtures of such metals which form an alloy with said precious metal and recovering said precious metal from said Imolten metal.

3. The method of claim 2 wherein said recovery of said precious metal comprises cooling said molten metal or a mixture of metals to its solid state, and thereafter recovering said precious metal from said solidified molten metal.

4. A method of obtaining a precious metal, said method comprising contacting a mixture of a rst and second metal in a molten state with an oily vapor containing said precious metal, said first and second metals selected from the class consisting of metals in Groups l-B, 2-B, 3-A, 4-A and S-A of the Periodic Table and which alloy with said precious metal, and recovering said precious metal from the resulting alloy.

5. The method of claim 4 wherein said rst and second metals are molten tin and molten aluminum.

6. The method of claim 4 wherein said first and second metals are molten zinc and molten aluminum.

7. The method of claim 4 wherein said first and second metals are molten zinc and molten lead.

8. The method of claim 2 wherein said molten metal contains mercury.

9. The method of claim 2 wherein said molten metal is zinc which is maintained at a molten temperature in excess of 790 F.

10. The method of claim 2 wherein said molten metal is lead which is maintained at a molten temperature in excess of `625" F.

11. The method of claim 2 wherein said molten metal is aluminum which is maintained at a molten temperature of about 1250 F.

12. The method of claim 2, wherein said precious metal is gold or silver or mixtures thereof, and said molten metal is tin.

References Cited UNITED STATES PATENTS 3,150,960 9/1964 Hunter 75-118 3,238,038 3/1966 Hunter 75-83 RICHARD O. DEAN, Primary Examiner U.S. Cl. X.R. 

